In a small bowl, whisk together the olive oil, lime juice, chopped chipotle in adobo, minced garlic, ground cumin, dried oregano, kosher salt, and black pepper to create the marinade.

Place the skirt steak in a large Ziploc bag or a shallow non-reactive dish. Pour the marinade over the steak, ensuring it's evenly coated. Seal the bag (or cover the dish) and refrigerate for at least 30 minutes, or up to 2 hours. Do not marinate for more than 4 hours, as the acidity can start to break down the meat too much.

While the steak is marinating, prepare your toppings: thinly slice or dice the red onion, chop the fresh cilantro, and dice or slice the avocados. Have your lime wedges, cotija cheese, crema, and salsa ready for serving.

Preheat your grill to high heat (about 450-500°F / 230-260°C). Lightly oil the grill grates to prevent sticking.

Remove the skirt steak from the marinade, letting any excess drip off. Discard the remaining marinade.

Place the skirt steak directly on the hot grill. Grill for 2-4 minutes per side for medium-rare (internal temperature 130-135°F / 54-57°C), or slightly longer for desired doneness. Skirt steak cooks quickly due to its thinness, so watch it closely.

Once cooked, transfer the skirt steak to a cutting board and tent it loosely with foil. Let it rest for 5-10 minutes. This allows the juices to redistribute, resulting in a more tender steak.

While the steak rests, warm the corn tortillas. You can do this by placing them directly on the grill for 15-30 seconds per side until pliable and slightly charred, or warm them in a dry frying pan/comal over medium heat.

Slice the rested skirt steak thinly against the grain. Cutting against the grain is crucial for tender skirt steak, as it shortens the muscle fibers.

Assemble your tacos: fill warm tortillas with sliced skirt steak, then top with red onion, cilantro, avocado, and a squeeze of fresh lime juice. Add crumbled cotija cheese, a drizzle of crema, and salsa if desired. Serve immediately and enjoy!